JPS6158462B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing acrylonitrile or methacrylonitrile by ammoxidizing propylene or isobutylene in the presence of a catalyst.
The main gist of the present invention relates to catalysts used in ammoxidation reactions. A method for producing acrylonitrile or methacrylonitrile by an ammoxidation reaction of propylene or isobutylene is well known, and many catalysts for use in the ammoxidation reaction have been proposed. For example, Tokuko Sho 36-5870, Tokko Sho 38-
A large number of catalysts for ammoxidation are disclosed in Japanese Patent Publication No. 17967, Japanese Patent Publication No. 58-2232, Japanese Patent Publication No. 48-43096, Japanese Patent Application Laid-Open No. 50-25528, etc. However, these known catalysts have the disadvantage of a relatively low ammonia efficiency. In other words, although the conversion rate of propylene or isobutylene to acrylonitrile or methacrylonitrile is large, the conversion rate of ammonia to acrylonitrile or methacrylonitrile is relatively small, which is still satisfactory in the present day when the price of ammonia is soaring. do not have. The present invention aims to provide a novel catalyst that exhibits excellent catalytic activity in terms of ammonia efficiency in producing acrylonitrile or methacrylonitrile. The present invention provides at least molybdenum, bismuth, iron, and component A (A is palladium, platinum, , osmium and iridium), and using an oxide catalyst containing 0.002 to 0.2 atoms of component A per 12 atoms of molybdenum. This is the manufacturing method. The catalyst of the present invention is characterized in that component A is used in a trace amount. The amount of component A is per 12 atoms of molybdenum
It is 0.002-0.2, preferably 0.005-0.1. If component A is smaller than this range, the ammonia yield (Y[NH ₃ ]) will not improve, and if it is larger than this range, complete oxidation by-product CO ₂ will increase, which is not preferable. The amount of bismuth or iron in the catalyst of the present invention is appropriately selected from the range of 0.5 to 10 per 12 molybdenum atoms. In addition to molybdenum, bismuth, iron, and component A, the catalyst of the present invention can contain an optional component selected from the following elements. alkali metals,
Alkaline earth metals, rare earth metals, Sn, Pb, Ti,
Zr, W, V, Nb, Cr, Mn, Co, Ni, Zn, Cu,
In, Tl, B, P and Sb can be used. The amount of these optional components is 10 atoms or less per 12 molybdenum atoms,
Preferably, 5 or less is appropriate, and potassium, rubidium and cesium are particularly suitable among alkali metals.
A value of 0.5 or less is preferable. The oxide catalyst of the present invention may contain neighboring components. Although the phosphorus component does not greatly affect the activity selectivity of the catalyst, it is known to be an effective additive component for stabilizing the slurry of the catalyst raw material and improving the wear resistance of the catalyst. The same effect of adding phosphorus components is also observed. Silica is preferably used as a carrier for the catalyst of the present invention. The silica content can be chosen in the range of 30-30% by weight. The catalyst can be prepared by a common method for preparing this type of catalyst. For example, it can be obtained by mixing an aqueous solution of a metal salt or an aqueous solution of nitric acid with a silica sol to obtain a slurry, followed by evaporation or spray drying, and finally calcination at a temperature selected from the range of 550°C to 750°C. can. Alternatively, first a catalyst containing no component A is obtained by the above method,
Then impregnating the precursor catalyst with a catalyst containing component A,
Finally, a method of firing at a temperature selected from the range of 350°C to 750°C is also suitable. The method of the present invention can be carried out in either a fluidized bed reaction or a fixed bed reaction. Propylene, isobutylene and ammonia do not necessarily need to be of high purity, and industrial grade raw materials can be used. Tertiary butanol can be used in place of isobutylene. Air is preferred as the oxygen source. The volume ratio of air to propylene or isobutylene is preferably in the range of 8 to 13. Although the required volume ratio of ammonia can be set within a wide range, it is preferably 1.0 to 1.15 for propylene, and 1.2 to 1.35 for isobutylene. If the volume ratio of ammonia is less than this range, the propylene yield or isobutylene yield will decrease, and conversely, if it is greater than this range, the ammonia yield will decrease.
The reaction temperature is preferably in the range of 400 to 500°C, particularly 410 to 480°C. The reaction pressure may be normal pressure, but the reaction may be carried out under increased pressure if necessary. The contact time between the raw material mixed gas and the catalyst is preferably in the range of 0.2 to 10 seconds, particularly 0.4 to 6 seconds. Examples of the present invention are shown below, but the scope of the present invention is not limited by these Examples. ₍ 1) Catalyst _preparation An oxide catalyst whose atomic _ratio composition of the metal component supported on 50% by weight of silica _is Pd _0.02 Mo ₁₂ Bi _4.1 Fe _7.2 K _0.07 P _1.0 was prepared _. It was prepared as follows. 166.7g of silica sol containing 30% by weight of _SiO2
and, under stirring, add 85% by weight phosphoric acid 1.73
Then add 32.07 g of ammonium hepta-molybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄・4H ₂ O] to 80 g of water.
Finally, add 29.83g of bismuth nitrate to 33g of 13% by weight nitric acid in advance.
(NO ₃ ) ₃・5H ₂ O] 43.93 g of ferric nitrate [Fe
(NO ₃ ) ₃ ·9H ₂ O] and 0.070 g of palladium nitrate [Pd(NO ₃ ) ₂ ] were added.
The raw material slurry obtained here was sent to a co-current spray dryer and dried at about 200°C. Atomization of the slurry was performed using an atomization device equipped with a dish-shaped rotor installed in the center of the upper part of the dryer. The obtained dry powder was transferred to a tunnel kiln and heated at 400 m
The catalyst was pre-calcined at 690°C for 1 hour and then 2 hours at 690°C. This catalyst is designated as 5-A. A catalyst having the same composition as Catalyst 5-A except that it did not contain Pd was prepared in the same manner as above. 20 g of the obtained catalyst was placed in a beaker, and 3 ml of an aqueous solution in which 0.014 g of palladium nitrate [Pd(NO ₃ ) ₂ ] was dissolved was added to impregnate the beaker.Finally, the beaker was calcined at 500° C. for 2 hours to obtain a catalyst. This catalyst is designated as 5-B. A catalyst of the present invention and a comparative catalyst were prepared in the same manner as Catalyst 5-A, and their compositions are shown in Table 1. If platinum, iridium or osmium is used as a catalyst component,
[ _H2PtCl6.6H2O ], _{[ IrCl4.H2O} ] or _{[ OsCl3 ]} was used. For other metals, ammonium salts, nitrates, or chlorides were used as appropriate. Further, the firing temperature of the catalyst was changed as appropriate depending on the catalyst as shown in Table 1.

【table】

[Table] (2) Unsaturated nitrile synthesis reaction (2-1) Synthesis of acrylonitrile The following propylene ammoxidation reaction was carried out using catalyst 5-A of the present invention and comparative catalyst 3 shown in Table 1. 2 g of each catalyst was packed into a Vycor glass reaction tube with an inner diameter of 8 mm, and a mixed gas of propylene, ammonia, oxygen, water vapor, and nitrogen was fed at a rate of 1.2 (NTP) per hour at a temperature of 460°C and under normal pressure.
It was passed at a flow rate of (converted). The composition of the mixed gas is determined by the volume ratio of oxygen to propylene.
1.9, and the volume ratio of water vapor to propylene was fixed at 1.0, and the volume ratio R of ammonia to propylene was varied in the range of 0.95 to 1.25. Further, the volume concentration of propylene in the mixed gas was adjusted to be diluted with nitrogen so that it was always 6%. The yield of acrylonitrile obtained as a result of this reaction is defined as the propylene yield (Y[C ₃ H ₆ ]) and the ammonia yield (Y
Evaluation was made using two indicators: [NH ₃ ]). Y [NH ₃ ] = Number of moles of acrylonitrile produced / Number of moles of propylene supplied × 100 Y [NH ₃ ] = Number of moles of acrylonitrile produced / Number of moles of ammonia supplied × 100 From the above definition, Y [C ₃ H ₆ ] and Y [NH ₃ ] is R
The relationship is Y[NH ₃ ]=Y[C ₃ H ₆ ]/R, where is the supply ratio of ammonia to propylene. The reaction results of the above two catalysts are shown in Table 2 below.

【table】

[Table] Table 2 shows that when the R=NH ₃ /C ₃ H ₆ ratio is decreased, Y[C ₃ H ₆ ] decreases, while Y[NH ₃ ] increases. Figure 1 shows Y based on the results in Table 1.
This diagram illustrates the relationship between [C ₃ H ₆ ] and Y[NH ₃ ], and shows that catalyst 5-A has an extremely superior ammonia yield compared to comparative catalyst 3.
For example, when Y[C ₃ H ₆ ]=84.0% constant, catalyst 1
-Y[NH ₃ ] of A is compared to that of the comparative catalyst
12% larger. A propylene ammoxidation reaction was carried out using the catalyst of the present invention and comparative catalyst shown in Table 1 according to the above method. However, the reaction temperature and raw material mixed gas flow rate were changed as appropriate depending on each catalyst. The results are shown in Table 3.

【table】

[Table] Catalyst 2 consists of molybdenum, bismuth, iron, phosphorus, which are the main components of the catalyst of the present invention, and a trace component A, and has a remarkable ammonia yield compared to Comparative Catalyst 1 which does not contain component A. shown to result in improved rates. Even in known catalysts containing optional components in addition to molybdenum, bismuth, iron, and phosphorus, the same effect is exhibited by including trace component A. This is shown in the relationships between comparative catalyst 3 and catalysts 4 to 9, comparative catalyst 10 and catalyst 11, comparative catalyst 12 and catalyst 13, comparative catalyst 14 and catalyst 15, and comparative catalyst 16 and catalyst 17. (2-2) Synthesis of methacrylonitrile The following isobutylene ammoxidation reaction was carried out using catalyst 43 of the present invention and comparative catalyst 41 shown in Table 1. 1 g of each catalyst was packed into a Vycor glass reaction tube with an inner diameter of 8 mm, and a mixed gas of isobutylene, ammonia, oxygen, water vapor, and nitrogen was fed at a rate of 1.2 (NTP) per hour at a temperature of 420°C and under normal pressure.
It was passed at a flow rate of (converted). The composition of the mixed gas is determined by the volume ratio of oxygen to isobutylene.
2.5, and the volume ratio of water vapor to isobutylene was fixed at 1.0, and the volume ratio R' of ammonia to isobutylene was varied in the range of 1.2 to 1.5. Further, the volume concentration of isobutylene in the mixed gas was adjusted to be diluted with nitrogen so that it was always 6%. The yield of methacrylonitrile obtained as a result of this reaction is determined by two indicators: isobutylene yield (Y[C ₄ H ₈ ]) and ammonia yield (Y′[NH ₃ ]) defined by the following formula. evaluated. Y [C ₄ H ₈ ] = Number of moles of methacrylonitrile produced / Number of moles of isobutylene supplied × 100 Y' [NH ₃ ] = Number of moles of methacrylonitrile produced / Number of moles of supplied ammonia × 100 From the above definition, Y [ C ₄ H ₈ ] and Y′ [NH ₃ ] are
where R′ is the supply ratio of ammonia to isobutylene, Y′[NH ₃ ]=Y[C ₄ H ₈ ]/
The relationship is R′. The reaction results of the above two catalysts are shown in Table 4 below.

[Table] Isobutylene ammoxidation reaction was carried out using the catalyst of the present invention and comparative catalyst shown in Table 1 according to the above method. However, the reaction temperature and raw material mixed gas flow rate were changed as appropriate depending on each catalyst. The results are shown in Table 5.

【table】 [Brief explanation of the drawing]

FIG. 1 is a diagram showing the correlation between propylene yield and ammonia yield.

Claims (1)

[Claims] 1. In producing acrylonitrile or methacrylonitrile by contacting propylene or isobutylene with ammonia and oxygen in the presence of a catalyst in the gas phase at high temperatures, at least molybdenum, bismuth, iron and component A (A is palladium, platinum, osmium) and iridium) and in which Component A is 0.002 to 0.2 atoms per 12 molybdenum atoms.